Adding strings in simulink

I'm using a simulink matlab function for the following code:

function [e1s,e2s,crits,users] = fcn(error1,error2)

n=32;

e1 = int2bit(error1,n,true);
e1r = reshape(e1,[8,4]);
e1s = flipud(e1r');

e2 = int2bit(error2,n,true);
e2r = reshape(e2,[8,4]);
e2s = flipud(e2r');

%% error to dashboard part
crits="Critical error:";
users="User error: "; 

crits =crits + " test";

I get the following two errors however:

Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.

Component:MATLAB Function | Category:Coder error

Size mismatch (size [1 x 15] ~= size [1 x 20]) in field 'Value'. Function 'MATLAB Function' (#89.286.291), line 17, column 1: "crits" Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

I don't understand why the output size suddenly is a vector. Is it just that simulink doesn't like strings?

Answer 1

[Walter Roberson]

you are resizing the string. string literals do not appear to be dynamically sized.

Use a different variable name the first time you assign to crits such as

cbm = "Critical error: ";
crits = cbm + test;

https://www.mathworks.com/help/simulink/ug/simulink-strings.html

[Nico Verbeek]

Thank you, this seems to work. The problem is that I want to add to the already existing string. This is because multiple error messages can be present at the same time. I want to then write if statements that add the different error messages to the string. Is this possible at all?

So I'll give a small snippet of my code (which is sadly just a bunch of if statements, didn't know how to do this differently) to give a better understanding of what I'm trying to do.

if e1s(3:4,:) ==1
   crits=crits+"  unknown critical error code"; 
end
if e1s(2,1:3) == 1
  crits=crits+"  12v min exceeded";
end
if e1s(1,1) == 1
   crits=crits+"  Hardware PWM tripzone";
end